Japanese Patent Publication No. 2004-270022A discloses the use of a nanopulse power source with a pulse width of not greater than 1000 nsec for forming diamond-like carbon films at atmospheric pressure.
Japanese Patent Publication No. H09 (1997)-312280A describes that the off-state time in pulse discharge be set at 0.5 μs to 30 μs to sustain pulse discharge. The duty ratio of the direct-current pulse voltage is high, namely not lower than 10%, and the so-called microwaves (high-frequency waves of 2.45 GHz) are pulsed.
Japanese Patent No. 3705977B mentions that the modulation period be 10 μs to 500 μs and the duty ratio be 10% to 80%. In this method, too, pulsed high-frequency waves of 0.4 MHz to 13.56 MHz are used as a plasma generation source in etching processes.
In Japanese Patent Publication No. 2005-159049A, a plasma generation method according to which the high-frequency cycle period is 10 kHz to 100 kHz and the duty ratio is 40% to 60% is utilized in film formation.
Japanese Patent Publication No. 2000-124190A describes a plasma source where the electron temperature is within the range of 0.25 eV to 1 eV; used as this plasma source are microwaves (0.3 GHz to 1 GHz).
In Japanese Patent No. 3639795B, an electron temperature of not higher than 3 eV and an electron density of not higher than 2×108 cm−3 are obtained by providing an electric power resulting from superposition of polarity inversion pulses. However, no control is imposed on the off-state time of pulses, and the electron density is very low.
Japanese Patent Publication No. 2003-234331A describes a method for plasma etching of organic material (low-k) films using an inorganic material film as a mask. It also describes that when a high plasma density is obtained, the self-bias also increases and, as a result, organic material films are damaged. Japanese Patent Publication No. 2001-118830A also describes about the damages.
Further, a process for ashing organic material (low-k) films is described in Japanese Patent Publication No. 2005-251837A.
And, Japanese Patent No. 3647303B describes a method of generating negative ions using temporal afterglow. Those negative ions are used for etching. Owing to the negative ions, abnormal etching patterns resulting from surface electrification, electrostatic breakdown of gate oxide films and/or deflected ions are avoided.
Moreover, a plasma ion implantation process is described in Japanese Patent (laid-open under PCT) Publication No. 2002-509641A. However, intermittent voltage application at 20 keV, for instance, results in increased thermal implantation into wafers, sometimes leading to progress of diffusion in excess of the desired implantation depth.
And an oxidation or nitriding process is described in WO2004/107430.